Testing electrode quality

ABSTRACT

A system includes a signal generator, configured to pass a generated signal, which has two different generated frequencies, through a circuit including an intrabody electrode. The system further includes a processor, configured to identify, while the generated signal is passed through the circuit, a derived frequency, which is derived from the generated frequencies, on the circuit, and to generate, in response to identifying the derived frequency, an output indicating a flaw in the electrode. Other embodiments are also described.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to another application entitled“DETECTING ASYMMERY IN A BIDIRECTIONAL SEMICONDUCOR DEVICE” (attorneyref. no. 1002-2170|ID-1790|BIO6343USNP1), filed on even date herewith,whose disclosure is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is related to the field of electronic circuitry,particularly for medical applications.

BACKGROUND

In many applications, symmetric bidirectional semiconductor devicescontrol the flow of electric current through a circuit.

SUMMARY OF THE INVENTION

There is provided, in accordance with some embodiments of the presentinvention, a system including a signal generator, configured to pass agenerated signal, which has two different generated frequencies, througha circuit including a bidirectional semiconductor device. The systemfurther includes a processor, configured to identify, while thegenerated signal is passed through the circuit, a derived frequency,which derives from the generated frequencies, on the circuit. Theprocessor is further configured to generate, in response to identifyingthe derived frequency, an output indicating that a property of thebidirectional semiconductor device is asymmetric.

In some embodiments, the processor is configured to identify the derivedfrequency over an electrophysiological channel belonging to the circuit.

In some embodiments, the derived frequency is within a bandwidth of anelectrophysiological signal carried over the electrophysiologicalchannel.

In some embodiments, each of the generated frequencies is outside thebandwidth.

In some embodiments, the property includes an impedance.

In some embodiments, the derived frequency is a difference between thegenerated frequencies.

In some embodiments, the processor is further configured to disable apower source connected to the circuit in response to detecting thederived frequency.

In some embodiments, the power source is selected from the group ofpower sources consisting of: a cardiac defibrillator, a cardiac pacer,and an ablation generator.

In some embodiments, the bidirectional semiconductor device belongs to avoltage suppressor.

In some embodiments, the bidirectional semiconductor device belongs to asemiconductor switch.

There is further provided, in accordance with some embodiments of thepresent invention, a method including passing a generated signal, whichhas two different generated frequencies, through a circuit including abidirectional semiconductor device.

The method further includes, while passing the two generated signalsthrough the circuit, identifying a derived frequency, which is derivedfrom the generated frequencies, on the circuit. The method furtherincludes, in response to identifying the derived frequency, generatingan output indicating that a property of the bidirectional semiconductordevice is asymmetric.

There is further provided, in accordance with some embodiments of thepresent invention, a system including a signal generator, configured topass a generated signal, which has two different generated frequencies,through a circuit including an intrabody electrode. The system furtherincludes a processor, configured to identify, while the generated signalis passed through the circuit, a derived frequency, which is derivedfrom the generated frequencies, on the circuit. The processor is furtherconfigured to generate, in response to identifying the derivedfrequency, an output indicating a flaw in the electrode.

In some embodiments, the derived frequency is a difference between thegenerated frequencies.

In some embodiments, each of the generated frequencies is less than 100Hz.

In some embodiments, an amplitude of the generated signal is less than50 μA.

In some embodiments, the signal generator is configured to pass thegenerated signal through the circuit while the electrode is submerged inan electrolytic solution.

In some embodiments, the electrolytic solution includes saline.

In some embodiments, the electrode belongs to an intrabody probe.

In some embodiments, the system further includes a kit including:

the signal generator; and

an electrical interface configured to connect the electrode to thesignal generator by connecting the kit to the probe.

In some embodiments, the kit further includes a communication interface,and the processor is configured to identify the derived frequency byprocessing an output signal received from the kit via the communicationinterface.

In some embodiments, the electrode is one of a plurality of electrodesbelonging to the probe, and the kit further includes a multiplexerconfigured to selectively connect the electrodes to the signalgenerator.

There is further provided, in accordance with some embodiments of thepresent invention, a method including passing a generated signal, whichhas two different generated frequencies, through a circuit including anintrabody electrode. The method further includes, while passing thegenerated signal through the circuit, identifying a derived frequency,which is derived from the generated frequencies, on the circuit. Themethod further includes, in response to detecting the derived frequency,generating an output indicating a flaw in the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

FIG. 1 is a schematic illustration of an electrophysiological system, inaccordance with some exemplary embodiments of the present invention;

FIG. 2 is a schematic illustration of circuitry, in accordance with someexemplary embodiments of the present invention; and

FIG. 3 is a schematic illustration of a system for testing electrodequality, in accordance with some exemplary embodiments of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS Glossary

In the context of the present application, including the claims, theterm “bidirectional semiconductor device” may refer to any semiconductordevice configured to conduct both the positive and negative portions ofan alternating current (AC) signal. If a property (e.g., the impedance)of the bidirectional semiconductor device is the same for both portionsof the signal, the property (or the device itself) is said to be“symmetric;” otherwise, the property (or the device itself) is said tobe “asymmetric.”

Overview

In many cases, it is desired that a bidirectional semiconductor devicein a circuit have symmetric properties, such that an alternating current(AC) passing through the device does not generate any direct current(DC) voltage. For a circuit connected to an intrabody probe, such as anelectrophysiological probe, disposed within the body of a subject, thissymmetry is particularly important, as any DC voltages generated, forexample, from the flow of ablative radiofrequency (RF) currents throughthe bidirectional semiconductor device, are likely to be dangerous tothe subject. Hence, there is a need for fast and effective detection ofany asymmetry in a bidirectional semiconductor device.

To address this need, exemplary embodiments of the present inventionprovide a system for testing the symmetry of a bidirectionalsemiconductor device in a circuit. The system comprises a signalgenerator connected to the circuit and configured to generate a signalhaving two different frequencies. Provided that the bidirectionalsemiconductor device is symmetric, the bidirectional semiconductordevice behaves as a linear device, and hence does not generate anyadditional frequencies. However, in the event that the bidirectionalsemiconductor device is asymmetric (e.g., by virtue of having anasymmetric impedance), the device behaves non-linearly, thus causingother “derived” frequencies, which derive from the frequencies of thegenerated signal, to be carried on the circuit. Hence, by identifyingone of these derived frequencies, such as the difference between thefrequencies of the generated signal, the asymmetry may be detected.

Advantageously, for electrophysiological applications, the derivedfrequencies may be detected over a preexisting electrophysiologicalchannel, such that the symmetry testing described herein may not requireadditional hardware. To facilitate this, the frequencies of thegenerated signal may be chosen such that the difference between thefrequencies falls within the bandwidth of the electrophysiologicalsignal carried over the channel. Nonetheless, the frequencies themselvesmay be chosen to fall outside this bandwidth, such that the generatedsignal does not interfere with the detection of the electrophysiologicalsignal.

Exemplary embodiments of the present invention further provide a testingkit for testing the quality of an electrode while the electrode issubmerged in an electrolytic solution. The kit, which comprises theaforementioned signal generator, is connected to the electrode, suchthat the generated signal flows through the electrode. In the event of aflaw in the surface of the electrode (e.g., in the event that thesurface is rough or dirty), the non-linearity of the interface betweenthe electrode and the electrolytic solution is increased, such that theamplitude with which derived frequencies are generated is alsoincreased. Hence, by identifying one of the derived frequencies, theflaw may be detected.

Although the present description mainly relates to electrophysiologicalapplications, it is emphasized that embodiments of the present inventionmay be used to test the symmetry of any bidirectional semiconductordevice, and to test the quality of any electrode.

System Description

Reference is initially made to FIG. 1, which is a schematic illustrationof an electrophysiological system 20, in accordance with some exemplaryembodiments of the present invention.

System 20 comprises an intrabody probe 26, comprising one or moreintrabody electrodes 28 disposed at the distal end thereof. Using probe26 and electrodes 28, a physician 30 may acquire electrophysiologicalsignals from a subject 22, such as electrogram signals from the heart 24of subject 22. Alternatively or additionally, the physician 30 may usethe probe 26 and electrodes 28 to pace or to defibrillate heart 24, orto ablate tissue of the heart 24.

Probe 26 is proximally connected to circuitry 34, which is typicallycontained in a console 32. Typically, system 20 further comprises aprocessor 38 and a monitor 36. In response to output from circuitry 34,processor 38 may display relevant output on monitor 36, as furtherdescribed below with reference to FIG. 2.

In general, processor 38 may be embodied as a single processor, or as acooperatively networked or clustered set of processors. In someexemplary embodiments, the functionality of processor 38, as describedherein, is implemented solely in hardware, e.g., using one or moreApplication-Specific Integrated Circuits (ASICs) or Field-ProgrammableGate Arrays (FPGAs). In other exemplary embodiments, the functionalityof processor 38 is implemented at least partly in software. For example,in some exemplary embodiments, processor 38 is embodied as a programmeddigital computing device comprising at least a central processing unit(CPU) and random-access memory (RAM). Program code, including softwareprograms, and/or data are loaded into the RAM for execution andprocessing by the CPU. The program code and/or data may be downloaded tothe processor in electronic form, over a network, for example.Alternatively or additionally, the program code and/or data may beprovided and/or stored on non-transitory tangible media, such asmagnetic, optical, or electronic memory. Such program code and/or data,when provided to the processor, produce a machine or special-purposecomputer, configured to perform the tasks described herein.

Reference is now made to FIG. 2, which is a schematic illustration ofcircuitry 34, illustrated in FIG. 1, in accordance with some exemplaryembodiments of the present invention.

Circuitry 34 comprises at least one digitizer 40, configured to digitizeelectrophysiological signals from the electrodes 28 and to output thedigitized signals 66 to processor 38 (FIG. 1) over a wired or wirelessconnection. Digitizer 40 may comprise any suitable filters for filteringthe signals prior to digitization.

Typically, circuitry 34 further comprises at least one power sourceconfigured to deliver power to the electrodes. For example, circuitry 34may comprise a cardiac pacer 42, a cardiac defibrillator, and/or anablation generator. Typically, the circuitry further comprises at leastone voltage suppressor 48, which suppresses voltages delivered by thepower source.

For exemplary embodiments in which the probe comprises multipleelectrodes, the circuitry typically comprises different respectiveelectrophysiological channels for the electrodes. Each channel comprisesa separate digitizer 40 and voltage suppressor 48, which are typicallyconnected to the electrode, in parallel to one another, via a resistor64. Circuitry 34 may further comprise a multiplexer 52, which comprisesmultiple semiconductor switches 46, and a multiplexer controller 44.Multiplexer controller 44 is configured to control switches 46 so as toselectively connect the channels to the power source.

In general, the circuitry may comprise any number of electrodes, andhence, any number of channels. By way of example, FIG. 2 shows anexemplary embodiment in which the probe comprises two electrodes,referred to in the figure as “electrode 1” and “electrode 2,” andcircuitry 34 correspondingly comprises two channels, referred to in thefigure as “channel 1” and “channel 2.”

Circuitry 34 comprises at least one bidirectional semiconductor device.

For example, each switch 46 may comprise a bidirectional semiconductordevice. As a specific example, each switch 46 may comprise alight-emitting diode (LED) 58 along with a pair of phototransistors 54connected to one another and to a pair of parasitic diodes 56. Inresponse to a control signal from multiplexer controller 44, LED 58 mayemit light toward phototransistors 54, thus causing the phototransistorsto become conductive. Current (e.g., from pacer 42) may then flowthrough the switch.

Alternatively or additionally, each voltage suppressor 48 may comprise abidirectional semiconductor device. For example, each voltage suppressor48 may comprise a pair of diodes 60 or thyristors connected to oneanother, in series or in parallel, in opposing orientations. Diodes 60may comprise avalanche or Zener diodes, for example.

Advantageously, circuitry 34 is configured to test the symmetry of anyof the bidirectional semiconductor devices belonging to the circuitry.To facilitate this testing, the circuitry comprises at least one signalgenerator 50 configured to generate a signal having a first frequency f1and a second frequency f2. Typically, the amplitude of the generatedsignal is relatively low, such as less than 10 μA, so as not to pose arisk to the subject. In the event that the impedance or another property(e.g., the cutoff voltage) of one of the bidirectional semiconductordevices is asymmetric, the device behaves non-linearly, thus generatingother frequencies derived from f1 and f2, such as frequencies that arelinear combinations of f1 and f2. By identifying one of these otherfrequencies, such as the beat frequency |f1−f2|, f1+f2, 2f1+f2, or|2f1−f2|, in digitized signal 66, the processor may detect theasymmetry.

In some exemplary embodiments, signal generator 50 comprises a voltagesource. In such embodiments, as shown in FIG. 2, the signal generatormay be modeled as a first voltage source 50 a, configured to generate afirst signal having first frequency f1, and a second voltage source 50b, configured to generate a second signal having second frequency f2,each of the voltage sources being connected in series with a respectiveresistor 62. In other exemplary embodiments, signal generator 50comprises a current source.

In some exemplary embodiments, circuitry 34 comprises a differentrespective signal generator for each channel. In other exemplaryembodiments, a single signal generator is connected, via a multiplexer,to all of the channels.

Typically, f1 and f2 lie outside the bandwidth of (i.e., outside therange of frequencies exhibited by) the electrophysiological signalcarried over the channel, such that the generated signal does notinterfere with the processing of the electrophysiological signal. Forexample, for applications in which electrogram signals are carried overthe channels, each of the generated frequencies may be greater than 500Hz, such as greater than 1000 Hz. Nevertheless, at least one derivedfrequency, such the difference between f1 and f2, is typically withinthe aforementioned bandwidth, such that the sampling rate of thedigitizer, which generally corresponds to the highest frequency in thebandwidth, is sufficient for capturing the derived frequency. Forexample, for electrogram applications, the derived frequency may be lessthan 500 Hz, such as between 400 and 500 Hz. Thus, advantageously, thederived frequency may be identified in signal 66, i.e., the regulardigitized electrophysiological signal received from digitizer 40.

In response to identifying the derived frequency (e.g., in response toidentifying a component of signal 66 having the derived frequency and anamplitude greater than a predefined threshold), the processor maygenerate an output indicating that the impedance of the bidirectionalsemiconductor device is asymmetric, e.g., by displaying a suitablewarning on monitor 36 (FIG. 1). Alternatively or additionally, inresponse to identifying the derived frequency, the processor may disablethe power source.

Testing Electrode Quality

Reference is now made to FIG. 3, which is a schematic illustration of asystem 67 for testing the quality of electrodes 28 prior to the use ofprobe 26, in accordance with some exemplary embodiments of the presentinvention.

System 67 comprises signal generator 50, which as set forth above withrespect to FIG. 2, may be modeled as a first voltage source 50 a,configured to generate a first signal having first frequency f1, and asecond voltage source 50 b, configured to generate a second signalhaving second frequency f2, each of the voltage sources being connectedin series with a respective resistor 62, and digitizer 40, which isconfigured to communicate with a processor 82 over a wired or wirelessconnection. To test each electrode, the generated signal from the signalgenerator is passed through a circuit including the electrode. While thegenerated signal is passed through the circuit, processor 82 monitorsthe circuit for a derived frequency, such as |f1−f2|, by processingdigitized signal 66, as described above with reference to FIG. 2. Inresponse to identifying the derived frequency (e.g., in response toidentifying a component of signal 66 having the derived frequency and anamplitude greater than a predefined threshold), the processor 82generates an output indicating a flaw in the electrode.

Typically, the signal generator and digitizer belong to a testing kit 76configured to connect to the probe 26, e.g., to the proximal endthereof. Typically, testing kit 76 further comprises multiplexer 52(which may comprise switches of any type) and multiplexer controller 44.Each switch in multiplexer 52 is configured to connect, via a differentrespective wire, to a different respective electrode at the distal endof the probe 26. The wires may be contained in a cable 86, which may beconnected to the probe via a suitable interface in a handle 74 of theprobe 26. In response to a control signal 80 from processor 82,multiplexer controller 44 controls multiplexer 52 such that themultiplexer selectively connects the electrodes to the signal generatorfor testing.

In general, processor 82 may be embodied as a single processor, or as acooperatively networked or clustered set of processors. In someexemplary embodiments, the functionality of processor 82, as describedherein, is implemented solely in hardware, e.g., using one or moreApplication-Specific Integrated Circuits (ASICs) or Field-ProgrammableGate Arrays (FPGAs). In other exemplary embodiments, the functionalityof processor 82 is implemented at least partly in software, as describedabove for processor 38 (FIG. 1). Processor 82 may belong to testing kit76 or, as implied by FIG. 3, to an external computer. In response toidentifying the derived frequency, the processor 82 may display asuitable warning on a computer monitor, output an audio alert, and/orgenerate another output, such as by activating a warning light belongingto the testing kit.

Typically, electrodes 28 are tested while submerged in an electrolyticsolution 70, such as saline, which simulates an intrabody environment.The non-linearity of the impedance at the interface between eachelectrode and solution 70, and hence, the amplitude of anyderived-frequency components of signal 66, increases with the degree towhich the surface of the electrode is flawed, e.g., rough or dirty.Hence, as described above, flaws may be detected in response toidentifying the derived frequencies in signal 66.

Typically, a return electrode 72, which is typically disposed at thebottom of the container 68 containing solution 70, is connected, via awire 84, to the testing kit. (Wire 84 may be contained in a cable.)Thus, the testing circuit through which the generated signal is passedincludes solution 70, return electrode 72, and wire 84.

In general, the testing kit may comprise a case made of any suitablematerial, such as a plastic, configured to hold the various componentsof the kit described herein. The testing kit may comprise any suitableelectrical interface, such as a port or socket, for connecting the kitto the probe such that electrodes 28 are connected to the signalgenerator. Similarly, the testing kit may comprise any suitableelectrical interface for connecting the kit to return electrode 72.Alternatively or additionally, the testing kit may comprise any suitablewired or wireless communication interface (e.g., a Universal Serial Bus(USB) port) for communicating with processor 82, such that the processormay receive signal 66 from the kit, and/or the kit may receive controlsignal 80 from the processor, via the communication interface.

Typically, frequencies f1 and f2 are relatively small, such as less than100 Hz, so as to amplify any non-linear response of the electrodes. Alsotypically, the amplitude of each of the generated signals is relativelysmall, such as less than 50 μA, so as to minimize any undesired effectson the electrode surfaces.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of embodiments of the presentinvention includes both combinations and sub combinations of the variousfeatures described hereinabove, as well as variations and modificationsthereof that are not in the prior art, which would occur to personsskilled in the art upon reading the foregoing description. Documentsincorporated by reference in the present patent application are to beconsidered an integral part of the application except that to the extentany terms are defined in these incorporated documents in a manner thatconflicts with the definitions made explicitly or implicitly in thepresent specification, only the definitions in the present specificationshould be considered.

1. A system for testing electrode quality, the system comprising: asignal generator, configured to pass a generated signal, which has twodifferent generated frequencies, through a circuit including anintrabody electrode; and a processor, configured to: while the generatedsignal is passed through the circuit, identify a derived frequency,which is derived from the generated frequencies, on the circuit, and inresponse to identifying the derived frequency, generate an outputindicating a flaw in the electrode.
 2. The system according to claim 1,wherein the derived frequency is a difference between the generatedfrequencies.
 3. The system according to claim 1, wherein each of thegenerated frequencies is less than 100 Hz.
 4. The system according toclaim 1, wherein an amplitude of the generated signal is less than 50μA.
 5. The system according to claim 1, wherein the signal generator isconfigured to pass the generated signal through the circuit while theelectrode is submerged in an electrolytic solution.
 6. The systemaccording to claim 5, wherein the electrolytic solution includes saline.7. The system according to claim 1, wherein the electrode belongs to anintrabody probe.
 8. The system according to claim 7, further comprisinga kit comprising: the signal generator; and an electrical interfaceconfigured to connect the electrode to the signal generator byconnecting the kit to the probe.
 9. The system according to claim 8,wherein the kit further comprises a communication interface, and whereinthe processor is configured to identify the derived frequency byprocessing an output signal received from the kit via the communicationinterface.
 10. The system according to claim 8, wherein the electrode isone of a plurality of electrodes belonging to the probe, and wherein thekit further comprises a multiplexer configured to selectively connectthe electrodes to the signal generator.
 11. A method for testingelectrode quality, the method comprising: passing a generated signal,which has two different generated frequencies, through a circuitincluding an intrabody electrode; while passing the generated signalthrough the circuit, identifying a derived frequency, which is derivedfrom the generated frequencies, on the circuit; and in response todetecting the derived frequency, generating an output indicating a flawin the electrode.
 12. The method according to claim 11, wherein thederived frequency is a difference between the generated frequencies. 13.The method according to claim 11, wherein each of the generatedfrequencies is less than 100 Hz.
 14. The method according to claim 11,wherein an amplitude of the generated signal is less than 50 μA.
 15. Themethod according to claim 11, wherein passing the generated signalthrough the circuit comprises passing the generated signal through thecircuit while the electrode is submerged in an electrolytic solution.16. The method according to claim 15, wherein the electrolytic solutionincludes saline.
 17. The method according to claim 15, wherein theelectrode belongs to an intrabody probe.
 18. The method according toclaim 17, wherein the signal generator belongs to a kit, and whereinpassing the generated signal through the circuit comprises passing thegenerated signal through the circuit while the kit is connected to theprobe.
 19. The method according to claim 18, wherein identifying thederived frequency comprises identifying the derived frequency byprocessing an output signal received from the kit.
 20. The methodaccording to claim 18, wherein the electrode is one of a plurality ofelectrodes belonging to the probe, and wherein the kit further includesa multiplexer configured to selectively connect the electrodes to thesignal generator.